The research plan explores fundamental questions related to the role of nitric oxide (NO) in cytokine-induced lung injury. Derangements in pulmonary vasomotor and endothelial function are prominent in this pathophysiology. Many of these sequelae are reproduced by the inflammatory cytokines which in turn influence the production of NO by constitutive (cNOS) and inducible (iNOS) nitric oxide synthases. The role of these isoforms, however, is not clear. Nonspecific inhibition of the enzymes has yielded both beneficial and injurious results. Our overall hypothesis is that transient cytotoxic NO production by iNOS mediates cellular dysfunction and damage while continued physiologic production of NO by cNOS maintains homeostasis and is protective during cytokine induced lung injury. We first evaluate cultures of pulmonary arterial microvascular smooth muscle and endothelial cells where cytokine stimulated NO synthase expression and associated cytotoxicity are defined. We then selectively alter NO production by the different isoforms and evaluate the resulting cytotoxicity and cellular dysfunction. Specifically, we inhibit iNOS in cytokine exposed cultures with aminoguanidine and anti sense oligonucleotides, and we simulate iNOS induction in cultures without cytokines by iNOS transfection and the addition of the NO donor S-nitroso-N-acetylpencillamine. In parallel, we inhibit cNOS in cytokine exposed cultures with antisense oligonucleotides and L-N(omega)-nitroarginine, and we stimulate cNOS activity by transfection.